Temperature sensors

ABSTRACT

A temperature sensor can include a resistor, a first electrical contact at a first end of the resistor, a second electrical contact at a second end of the resistor, and a resistance measuring device. The resistor can be formed of a matrix of sintered elemental transition metal particles interlocked with a matrix of fused thermoplastic polymer particles. The resistance measuring device can be connected to the first electrical contact and the second electrical contact to measure a resistance of the resistor.

BACKGROUND

Certain types of temperature sensors can measure temperatures based onchanges in electrical resistance of a material. The material is oftenreferred to as a “thermistor” or thermally sensitive resistor.Thermistors are often made of a semiconducting material such as metaloxides or silicon. Depending on the material, a thermistor can have apositive or negative temperature coefficient. In positive temperaturecoefficient thermistors, the resistance of the material increases astemperature rises. Conversely, in a negative temperature coefficientthermistor, the resistance of the material decreases as temperaturerises. Thermistors can be used in applications such as temperaturesensors, current limiters in electrical circuits, self-regulatingheating elements, and so on. A typical thermistor can include athermistor chip made of the temperature sensitive material, wiresleading to two sides of the thermistor chip, and an insulating beadencapsulating the thermistor chip.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a 3-dimensional printed temperature sensorin accordance with examples of the present disclosure;

FIG. 2 is a top plan view of a 3-dimensional printed part having anintegrated temperature sensor in accordance with examples of the presentdisclosure;

FIG. 3 is a close-up side cross-sectional view of a layer ofthermoplastic polymer powder with a conductive fusing agent compositionand a second fusing agent composition in accordance with examples of thepresent disclosure;

FIG. 4 is a close-up side cross-sectional view of the layer of FIG. 3after the conductive fusing agent composition and second fusing agentcomposition have been deposited onto the layer;

FIG. 5 is a close-up side cross-sectional view of the layer of FIG. 4after the layer has been fused;

FIG. 6 is a flow chart illustrating a method of making a 3-dimensionalprinted part having an integrated temperature sensor in accordance withexamples of the present disclosure; and

FIG. 7 is a graph of resistance vs. time for a 3-dimensional printedtemperature sensor at a variety of temperatures in accordance withexamples of the present disclosure.

The figures depict several examples of the presently disclosedtechnology. However, it should be understood that the present technologyis not limited to the examples depicted.

DETAILED DESCRIPTION

The present disclosure is drawn to the area of temperature sensors and3D printing. More specifically, the present disclosure provides3-dimensional printed temperature sensors, 3-dimensional printed partswith integrated temperature sensors, and methods of printing the parts.

Thermistors are typically discrete components that can be connected to acircuit by soldering, such as on a printed circuit board. In contrast,the present technology provides thermally sensitive resistors that canbe embedded as a part of a 3-dimensional printed part. By eliminatingthe thermistor as a separate component, the complexity and cost of asystem using the thermistor can be reduced. Potential cost efficienciesinclude the elimination of manufacturing steps and material costs. Thepresent technology can also improve reliability and durability ofsystems by reducing instances of failure due to damage or separation ofa thermistor. Integrating temperature sensors as a part of 3-dimensionalprinted objects also allows for measuring of internal temperatures atany internal location in the part. This can provide advantages oversurface mounted temperature sensors, which measure temperature on thesurface where the sensor is attached. Additionally, installing sensorsinternally in an object is normally accomplished by drilling a hole orotherwise forming a void space within the object into which a sensor isinserted. Such modifications of the object can impair surface finish orweaken the structural integrity of the object. In contrast, thetemperature sensors described herein can be an integral part of a3-dimensional printed object. Thus, the temperature sensors can beformed at any internal location in the object without substantiallyweakening the object.

In some examples of the present technology, 3-dimensional printed partswith integrated temperature sensors can be formed using a processinvolving a powder bed of thermoplastic polymer particles, a conductivefusing agent composition, and a second fusing agent composition. In thisprocess, a thin layer of polymer powder is spread to form a powder bed.A printing head, such as an inkjet print head, is then used to printfusing agent compositions over portions of the powder bed correspondingto a thin layer of the three dimensional object to be formed. With eachlayer, a conductive fusing agent composition can be printed in areaswhere a conductive resistor for the temperature sensor is desired to beformed, and a second fusing agent composition can be printed in otherareas. The bed can then be exposed to a radiation source, e.g.,typically the entire bed. The fusing agent compositions absorb moreenergy from the radiation source than the unprinted powder. The absorbedradiation can then be converted to thermal energy, causing the printedportions of the powder to melt and coalesce. This forms a solid layer.After the first layer is formed, a new thin layer of polymer powder canbe spread over the powder bed and the process is repeated to formadditional layers until a complete 3-dimensional part is printed. Such3-dimensional printing processes can achieve fast throughput with goodaccuracy.

In one example, a temperature sensor can include a resistor formed of amatrix of sintered elemental transition metal particles interlocked witha matrix of fused thermoplastic polymer particles, wherein the resistorhas a positive temperature coefficient of resistance. The sensor canalso include a first electrical contact at a first end of the resistor,a second electrical contact at a second end of the resistor, and aresistance measuring device connected to the first electrical contactand the second electrical contact to measure a resistance of theresistor. In certain specific examples, the elemental transition metalparticles can include silver particles, copper particles, goldparticles, or combinations thereof. In other examples, the matrix offused thermoplastic polymer particles can include a fusing agentselected from carbon black, a near-infrared absorbing dye, anear-infrared absorbing pigment, a tungsten bronze, a molybdenum bronze,metal nanoparticles, a conjugated polymer, or combinations thereof. Theresistor can include a halogen salt in the matrix of sintered elementaltransition metal particles, the matrix of fused thermoplastic polymerparticles, or both. Resistors used in the temperature sensors describedherein can, in some examples, have a resistance from 1 ohm to 1 Megaohm.

In another example of the present technology, a 3-dimensional printedpart having an integrated temperature sensor can include a part bodyformed of fused thermoplastic polymer particles, and a resistor formedof a matrix of sintered elemental transition metal particles interlockedwith a matrix of fused thermoplastic polymer particles. The matrix offused thermoplastic polymer particles can be continuously fused to thefused thermoplastic polymer particles of the part body, and the resistorhas a positive temperature coefficient of resistance. The 3-dimensionalprinted part can also include a first electrical contact at a first endof the resistor, a second electrical contact at a second end of theresistor, and a resistance measuring device connected to the firstelectrical contact and the second electrical contact to measure aresistance of the resistor. In certain examples of the 3-dimensionalprinted parts can have integrated temperature sensors, and the elementaltransition metal particles can include silver particles, copperparticles, gold particles, or combinations thereof. In further examples,the fused thermoplastic polymer particles can include a fusing agentselected from carbon black, a near-infrared absorbing dye, anear-infrared absorbing pigment, a tungsten bronze, a molybdenum bronze,metal nanoparticles, a conjugated polymer, or combinations thereof. Instill further examples, the resistor can also include a halogen salt inthe matrix of sintered elemental transition metal particles, the matrixof fused thermoplastic polymer particles, or both. A resistor can alsobe formed as a part of the 3-dimensional printed part according tocertain examples of the present technology, and can have a resistancefrom 1 ohm to 1 Mega ohm. In some specific examples, the resistor can beembedded in the part body of the 3-dimensional printed part. In furtherexamples, the 3-dimensional printed part can be formed of multiplelayers of fused thermoplastic polymer particles stacked in a z-axisdirection, and the resistor can be oriented at least partially in thez-axis direction.

Another example of the present technology can include a method of makinga 3-dimensional printed part having an integrated temperature sensor.The method can include steps of dispensing a conductive fusing agentcomposition including a transition metal onto a first area of a layer ofthermoplastic polymer particles, and dispensing a second fusing agentcomposition onto a second area of the layer of thermoplastic polymerparticles. The second fusing agent composition can include a fusingagent capable of absorbing electromagnetic radiation to produce heat. Anadditional step can include fusing the first and second areas withelectromagnetic radiation to form a resistor in the first area and apart body in the second area, wherein the resistor includes a matrix ofsintered transition metal particles interlocked with a matrix of fusedthermoplastic polymer particles, and the part body includes fusedthermoplastic polymer particles, and wherein the resistor has a positivetemperature coefficient of resistance. Another step can includeconnecting a resistance measuring device to the resistor to measure aresistance of the resistor. In a specific example of the method, theresistor can be embedded in the part body. In another example of themethod, the transition metal can be in the form of elemental transitionmetal particles.

With this description in mind, FIG. 1 shows an example of a temperaturesensor 100. The temperature sensor, which can be a 3-dimensional printedtemperature sensor, can include a resistor 110, a first electricalcontact 120 at a first end of the resistor, and a second electricalcontact 130 at a second end of the resistor. The resistor can be formedof a matrix of sintered elemental transition metal particles interlockedwith a matrix of fused thermoplastic polymer particles. This compositematerial including the matrix of sintered elemental transition metalparticles and the matrix of fused thermoplastic polymer particles willbe described in more detail below.

The present technology also extends to 3-dimensional printed partshaving an integrated temperature sensor. FIG. 2 shows an example of sucha 3-dimensional printed part 200. The part can include a part body 210formed of fused thermoplastic polymer particles. The integratedtemperature sensor can include a resistor 110, a first electricalcontact 120 at a first end of the resistor, and a second electricalcontact 130 at a second end of the resistor. As described above, theresistor can be formed of a matrix of sintered elemental transitionmetal particles interlocked with a matrix of fused thermoplastic polymerparticles. The matrix of fused thermoplastic polymer particles can becontinuously fused to the fused thermoplastic polymer particles of thepart body.

The conductive composite material making up the resistor is shown inmore detail in FIGS. 3-5. To form the resistor, as shown in FIG. 3, alayer 300 of thermoplastic polymer powder particles 310 can be treatedwith a conductive fusing agent composition 320 in a first portion 330 ofthe layer, and a second fusing agent composition 340 can be dispensedonto a second portion 350 of the layer. The conductive fusing agentcomposition can include a transition metal. The second fusing agentcomposition can include a fusing agent capable of absorbingelectromagnetic radiation to produce heat.

FIG. 4 shows the layer 300 of thermoplastic polymer particles 310 afterthe conductive fusing agent composition and second fusing agentcomposition have been applied. At this point the layer includestransition metal particles 425 and a fusing agent 445 in spaces betweenthermoplastic polymer particles in the first portion 330 and secondportion 350, respectively.

It should be noted that these figures are not necessarily drawn toscale, and the relative sizes of thermoplastic polymer particles andtransition metal particles can differ from those shown. For example, inmany cases the transition metal particles can be much smaller than thethermoplastic polymer particles, such as 2-3 orders of magnitudesmaller.

FIG. 5 shows the layer 300 after being cured. When the layer is cured byexposure to electromagnetic radiation, the transition metal particles inthe first portion 330 sinter together to form a matrix of sintered metalparticles 580. The thermoplastic polymer particles fuse together in boththe first portion and the second portion 350, forming a matrix of fusedthermoplastic polymer particles 590. The matrix of sintered metalparticles and the fused thermoplastic polymer particles in the firstportion are interlocked, forming the conductive composite. It should benoted that FIGS. 3-5 shows only a 2-dimensional cross-section of theconductive composite. Although the sintered metal particles appear to bein isolated locations in the figure, the matrix of sintered metalparticles can be a continuously connected matrix in three dimensions.Thus, the conductive composite can have good electrical conductivitythrough the matrix of sintered transition metal particles

A variety of materials can be used to form the 3-dimensional printedtemperature sensors and parts having integrated temperature sensors. Insome examples, the materials can include a thermoplastic polymer powder,a conductive fusing agent composition, and a second fusing agentcomposition. The thermoplastic polymer powder can include powderparticles with an average particle size from 20 μm to 100 μm. As usedherein, “average” with respect to properties of particles refers to anumber average unless otherwise specified. Accordingly, “averageparticle size” refers to a number average particle size. Additionally,“particle size” refers to the diameter of spherical particles, or to thelongest dimension of non-spherical particles.

In certain examples, the polymer particles can have a variety of shapes,such as substantially spherical particles or irregularly-shapedparticles. In some examples, the polymer powder can be capable of beingformed into 3D printed parts with a resolution of 20 to 100 microns. Asused herein, “resolution” refers to the size of the smallest featurethat can be formed on a 3D printed part. The polymer powder can formlayers from about 20 to about 100 microns thick, allowing the fusedlayers of the printed part to have roughly the same thickness. This canprovide a resolution in the z-axis direction of about 20 to about 100microns. The polymer powder can also have a sufficiently small particlesize and sufficiently regular particle shape to provide about 20 toabout 100 micron resolution along the x-axis and y-axis.

In some examples, the thermoplastic polymer powder can be colorless. Forexample, the polymer powder can have a white, translucent, ortransparent appearance. When used with a colorless fusing agentcomposition, such polymer powders can provide a printed part that iswhite, translucent, or transparent. In other examples, the polymerpowder can be colored for producing colored parts. In still otherexamples, when the polymer powder is white, translucent, or transparent,color can be imparted to the part by the fusing agent composition or acolored ink.

The thermoplastic polymer powder can have a melting or softening pointfrom about 70° C. to about 350° C. In further examples, the polymer canhave a melting or softening point from about 150° C. to about 200° C. Avariety of thermoplastic polymers with melting points or softeningpoints in these ranges can be used. For example, the polymer powder canbe selected from the group consisting of nylon 6 powder, nylon 9 powder,nylon 11 powder, nylon 12 powder, nylon 66 powder, nylon 612 powder,polyethylene powder, thermoplastic polyurethane powder, polypropylenepowder, polyester powder, polycarbonate powder, polyether ketone powder,polyacrylate powder, polystyrene powder, and mixtures thereof. In aspecific example, the polymer powder can be nylon 12, which can have amelting point from about 175° C. to about 200° C. In another specificexample, the polymer powder can be thermoplastic polyurethane.

The thermoplastic polymer particles can also in some cases be blendedwith a filler. The filler can include inorganic particles such asalumina, silica, or combinations thereof. When the thermoplastic polymerparticles fuse together, the filler particles can become embedded in thepolymer, forming a composite material. In some examples, the filler caninclude a free-flow agent, anti-caking agent, or the like. Such agentscan prevent packing of the powder particles, coat the powder particlesand smooth edges to reduce inter-particle friction, and/or absorbmoisture. In some examples, a weight ratio of thermoplastic polymerparticles to filler particles can be from 10:1 to 1:2 or from 5:1 to1:1.

A conductive fusing agent composition can be used to form portions of a3-dimensional printed part that will act as a resistor in thetemperature sensor. The conductive fusing agent composition can includea transition metal. When the conductive fusing agent composition isprinted onto a layer of the thermoplastic polymer powder, the conductivefusing agent composition can penetrate into the spaces between powderparticles. The layer can then be cured by exposing the layer toelectromagnetic radiation. The conductive fusing agent composition canfacilitate fusing of the powder particles by absorbing energy from theelectromagnetic radiation and converting the energy to heat. This raisesthe temperature of the powder above the melting or softening point ofthe thermoplastic polymer. Additionally, during printing, curing, orboth, the transition metal in the conductive fusing agent compositioncan form a conductive transition metal matrix that becomes interlockedwith the fused thermoplastic polymer particles.

In some examples, the transition metal in the conductive fusing agentcomposition can be in the form of elemental transition metal particles.The elemental transition metal particles can include, for example,silver particles, copper particles, gold particles, platinum particles,palladium particles, chromium particles, nickel particles, zincparticles, or combinations thereof. The particles can also includealloys of more than one transition metal, such as Au—Ag, Ag—Cu, Ag—Ni,Au—Cu, Au—Ni, Au—Ag—Cu, or Au—Ag—Pd.

In certain examples, other non-transition metals can be included inaddition to the transition metal. The non-transition metals can includelead, tin, bismuth, indium, gallium, and others. In some examples,soldering alloys can be included. The soldering alloys can includealloys of lead, tin, bismuth, indium, zinc, gallium, silver, copper, invarious combinations. In certain examples, such soldering alloys can beprinted in locations that are to be used as soldering connections forprinted electrical components. The soldering alloys can be formulated tohave low melting temperatures useful for soldering, such as less than230° C.

In further examples, the elemental transition metal particles can benanoparticles having an average particle size from 10 nm to 200 nm. Inmore specific examples, the elemental transition metal particles canhave an average particle size from 30 nm to 70 nm.

As metal particles are reduced in size, the temperature at which theparticles are capable of being sintered can also be reduced. Therefore,using elemental transition metal nanoparticles in the conductive fusingagent composition can allow the particles to sinter and form aconductive matrix of sintered nanoparticles at relatively lowtemperatures. For example, the elemental transition metal particles inthe conductive fusing agent composition can be capable of being sinteredat or below the temperature reached during curing in the 3-dimensionalprinting process. In a further example, the thermoplastic polymer powderbed can be heated to a preheat temperature during the printing process,and the elemental transition metal particles can be capable of beingsintered at or below the preheat temperature. In still further examples,the elemental transition metal particles can be capable of beingsintered at a temperature from 20° C. to 350° C. As used herein, thetemperature at which the elemental transition metal particles arecapable of being sintered refers to the lowest temperature at which theparticles will become sintered together, forming a conductive matrix ofsintered particles. It is understood that temperatures above this lowesttemperature will also cause the particles to become sintered.

In additional examples of the conductive fusing agent composition, thetransition metal can be in the form of elemental transition metalparticles that are stabilized by a dispersing agent at surfaces of theparticles. The dispersing agent can include ligands that passivate thesurface of the particles. Suitable ligands can include a moiety thatbinds to the transition metal. Examples of such moieties can includesulfonic acid, phosphonic acid, carboxylic acid, dithiocarboxylic acid,phosphonate, sulfonate, thiol, carboxylate, dithiocarboxylate, amine,and others. In some cases, the dispersing agent can contain an alkylgroup having from 3-20 carbon atoms, with one of the above moieties atan end of the alkyl chain. In certain examples, the dispersing agent canbe an alkylamine, alkylthiol, or combinations thereof. In furtherexamples, the dispersing agent can be a polymeric dispersing agent, suchas polyvinylpyrrolidone (PVP), polyvinylalcohol (PVA),polymethylvinylether, poly(acrylic acid) (PAA), nonionic surfactants,polymeric chelating agents, and others. The dispersing agent can bind tothe surfaces of the elemental transition metal particles throughchemical and/or physical attachment. Chemical bonding can include acovalent bond, hydrogen bond, coordination complex bond, ionic bond, orcombinations thereof. Physical attachment can include attachment throughvan der Waal's forces, dipole-dipole interactions, or a combinationthereof.

In further examples, the conductive fusing agent composition can includea transition metal in the form of a metal salt or metal oxide. Undercertain conditions, a transition metal salt or metal oxide in theconductive fusing agent composition can form elemental transition metalparticles in situ after being printed onto the thermoplastic polymerpowder bed. The elemental transition metal particles thus formed canthen be sintered together to form a conductive matrix. In some examples,a reducing agent can be reacted with the metal salt or metal oxide toproduce elemental metal particles. In one example, a reducing agent canbe underprinted onto the powder bed before the conductive fusing agentcomposition. In another example, a reducing agent can be overprintedover the conductive fusing agent composition. In either case, thereducing agent can be reacted with the metal salt or metal oxide to formelemental metal particles before the thermoplastic polymer particlelayer is cured. Suitable reducing agents can include, for example,glucose, fructose, maltose, maltodextrin, trisodium citrate, ascorbicacid, sodium borohydride, ethylene glycol, 1,5-pentanediol,1,2-propylene glycol, and others.

The concentration of transition metal in the conductive fusing agentcomposition can vary. However, higher transition metal concentrationscan tend to provide better conductivity due to a larger amount ofconductive material being deposited on the powder bed. In some examples,the conductive fusing agent composition can contain from about 5 wt % toabout 50 wt % of the transition metal, with respect to the entire weightof the conductive fusing agent composition. In further examples, theconductive fusing agent composition can contain from about 10 wt % toabout 30 wt % of the transition metal, with respect to the entire weightof the conductive fusing agent composition.

In some examples of the present technology, a pretreat composition canbe used with the conductive fusing agent composition. The pretreatcomposition can include a halogen salt, such as sodium chloride orpotassium chloride, for example. The halogen salt can react withdispersing agents at the surfaces of transition metal particles toremove the dispersing agents from the particles. This can increase thesintering between the metal particles and improve the conductivity ofthe matrix formed of the sintered particles. The pretreat compositioncan be dispensed onto the powder bed before the conductive fusing agentcomposition. When the conductive fusing agent composition is printedover the pretreat composition, the transition metal particles can comeinto contact with the halogen salt in the pretreat composition. Inalternate examples, the polymer powder can be pretreated with a halogensalt before being used in the 3-dimensional printing system. When theconductive fusing agent composition is printed onto the powder bed, thetransition metal particles in the conductive fusing agent compositioncan come into contact with the halogen salt already present on thepowder.

A second fusing agent composition can also be incorporated in thematerials used to make 3-dimensional printed temperature sensors andparts having integrated temperature sensors. In some examples, thesecond fusing agent composition can be devoid or substantially devoid ofthe transition metal contained in the conductive fusing agentcomposition. Thus, the second fusing agent composition can provide alower conductivity than the conductive fusing agent composition whenprinted on the thermoplastic polymer powder. However, in some examplesthe second fusing agent composition can include metal particles thatprovide a lower conductivity than the transition metal in the conductivefusing agent composition. For example, the second fusing agentcomposition can include metal particles with passivated surfaces that donot sinter together to form a conductive matrix.

The second fusing agent composition can contain another fusing agentthat is capable of absorbing electromagnetic radiation to produce heat.The fusing agent can be colored or colorless. In various examples, thefusing agent can be carbon black, near-infrared absorbing dyes,near-infrared absorbing pigments, tungsten bronzes, molybdenum bronzes,metal nanoparticles, or combinations thereof. Examples of near-infraredabsorbing dyes include aminium dyes, tetraaryldiamine dyes, cyaninedyes, pthalocyanine dyes, dithiolene dyes, and others. In furtherexamples, the fusing agent can be a near-infrared absorbing conjugatedpolymer such as poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS), a polythiophene, poly(p-phenylene sulfide), a polyaniline,a poly(pyrrole), a poly(acetylene), poly(p-phenylene vinylene),polyparaphenylene, or combinations thereof. As used herein, “conjugated”refers to alternating double and single bonds between atoms in amolecule. Thus, “conjugated polymer” refers to a polymer that has abackbone with alternating double and single bonds. In many cases, thefusing agent can have a peak absorption wavelength in the range of 800nm to 1400 nm.

The amount of fusing agent in the second fusing agent composition canvary depending on the type of fusing agent. In some examples, theconcentration of fusing agent in the second fusing agent composition canbe from 0.1 wt % to 20 wt %. In one example, the concentration of fusingagent in the second fusing agent composition can be from 0.1 wt % to 15wt %. In another example, the concentration can be from 0.1 wt % to 8 wt%. In yet another example, the concentration can be from 0.5 wt % to 2wt %. In a particular example, the concentration can be from 0.5 wt % to1.2 wt %.

The fusing agent can have a temperature boosting capacity sufficient toincrease the temperature of the polymer powder above the melting orsoftening point of the polymer powder. As used herein, “temperatureboosting capacity” refers to the ability of a fusing agent to convertnear-infrared light energy into thermal energy to increase thetemperature of the printed polymer powder over and above the temperatureof the unprinted portion of the polymer powder. Typically, the polymerpowder particles can be fused together when the temperature increases tothe melting or softening temperature of the polymer. As used herein,“melting point” refers to the temperature at which a polymer transitionsfrom a crystalline phase to a pliable, amorphous phase. Some polymers donot have a melting point, but rather have a range of temperatures overwhich the polymers soften. This range can be segregated into a lowersoftening range, a middle softening range and an upper softening range.In the lower and middle softening ranges, the particles can coalesce toform a part while the remaining polymer powder remains loose. If theupper softening range is used, the whole powder bed can become a cake.The “softening point,” as used herein, refers to the temperature atwhich the polymer particles coalesce while the remaining powder remainsseparate and loose. When the fusing agent composition is printed on aportion of the polymer powder, the fusing agent can heat the printedportion to a temperature at or above the melting or softening point,while the unprinted portions of the polymer powder remain below themelting or softening point. This allows the formation of a solid 3Dprinted part, while the loose powder can be easily separated from thefinished printed part.

Although melting point and softening point are often described herein asthe temperatures for coalescing the polymer powder, in some cases thepolymer particles can coalesce together at temperatures slightly belowthe melting point or softening point. Therefore, as used herein “meltingpoint” and “softening point” can include temperatures slightly lower,such as up to about 20° C. lower, than the actual melting point orsoftening point.

In one example, the fusing agent can have a temperature boostingcapacity from about 10° C. to about 70° C. for a polymer with a meltingor softening point from about 100° C. to about 350° C. If the powder bedis at a temperature within about 10° C. to about 70° C. of the meltingor softening point, then such a fusing agent can boost the temperatureof the printed powder up to the melting or softening point, while theunprinted powder remains at a lower temperature. In some examples, thepowder bed can be preheated to a temperature from about 10° C. to about70° C. lower than the melting or softening point of the polymer. Thefusing agent composition can then be printed onto the powder and thepowder bed can be irradiated with a near-infrared light to coalesce theprinted portion of the powder.

In some examples of the present technology, the conductive fusing agentcomposition and the second fusing agent composition can be balanced sothat thermoplastic polymer powder that is printed with the conductivefusing agent composition and the second fusing agent composition reachnearly the same temperature when exposed to light during curing. Thetype and amount of fusing agent in the second fusing agent compositioncan be selected to match the temperature boosting capacity of thetransition metal in the conductive fusing agent composition. The typeand amount of transition metal in the conductive fusing agentcomposition can also be adjusted to match the temperature boostingcapacity of the fusing agent in the second fusing agent composition.Additionally, in some examples the conductive fusing agent compositioncan contain another fusing agent other than the transition metal. Incertain examples, the conductive fusing agent composition and the secondfusing agent composition can raise the temperature of the thermoplasticpolymer powder to temperatures within 30° C., within 20° C., or within10° C. of each other during curing.

In further examples, colored inks can also be used for adding color tothe thermoplastic polymer powder. This can allow for printing offull-color 3-dimensional parts. In one example, the cyan, magenta,yellow, and black inks can be used in addition to the conductive fusingagent composition, second fusing agent composition, and pretreatcomposition if present.

Each of the conductive fusing agent composition, pretreat composition,second fusing agent composition, and additional colored inks can beformulated for use in a fluid jet printer such as an ink jet printer.The transition metal and fusing agents can be stable in a liquid jettingvehicle and the inks can provide good jetting performance. In someexamples, the transition metal and fusing agents can be water-soluble,water-dispersible, organic-soluble, or organic-dispersible. Thetransition metal and fusing agents can also be compatible with thethermoplastic polymer powder so that jetting the compositions onto thepolymer powder provides adequate coverage and penetration of thetransition metal and fusing agents into the powder.

Any of the above described compositions can also include a pigment ordye colorant that imparts a visible color to the compositions. In someexamples, the colorant can be present in an amount from 0.5 wt % to 10wt % in the compositions. In one example, the colorant can be present inan amount from 1 wt % to 5 wt %. In another example, the colorant can bepresent in an amount from 5 wt % to 10 wt %. However, the colorant isoptional and in some examples the compositions can include no additionalcolorant. These compositions can be used to print 3D parts that retainthe natural color of the polymer powder. Additionally, the compositionscan include a white pigment such as titanium dioxide that can alsoimpart a white color to the final printed part. Other inorganic pigmentssuch as alumina or zinc oxide can also be used.

In some examples, the colorant can be a dye. The dye may be nonionic,cationic, anionic, or a mixture of nonionic, cationic, and/or anionicdyes. Specific examples of dyes that may be used include, but are notlimited to, Sulforhodamine B, Acid Blue 113, Acid Blue 29, Acid Red 4,Rose Bengal, Acid Yellow 17, Acid Yellow 29, Acid Yellow 42, AcridineYellow G, Acid Yellow 23, Acid Blue 9, Nitro Blue Tetrazolium ChlorideMonohydrate or Nitro BT, Rhodamine 6G, Rhodamine 123, Rhodamine B,Rhodamine B Isocyanate, Safranine O, Azure B, and Azure B Eosinate,which are available from Sigma-Aldrich Chemical Company (St. Louis,Mo.). Examples of anionic, water-soluble dyes include, but are notlimited to, Direct Yellow 132, Direct Blue 199, Magenta 377 (availablefrom Ilford AG, Switzerland), alone or together with Acid Red 52.Examples of water-insoluble dyes include azo, xanthene, methine,polymethine, and anthraquinone dyes. Specific examples ofwater-insoluble dyes include Orasol® Blue GN, Orasol® Pink, and Orasol®Yellow dyes available from Ciba-Geigy Corp. Black dyes may include, butare not limited to, Direct Black 154, Direct Black 168, Fast Black 2,Direct Black 171, Direct Black 19, Acid Black 1, Acid Black 191, MobayBlack SP, and Acid Black 2.

In other examples, the colorant can be a pigment. The pigment can beself-dispersed with a polymer, oligomer, or small molecule; or can bedispersed with a separate dispersant. Suitable pigments include, but arenot limited to, the following pigments available from BASF: Paliogen®)Orange, Heliogen® Blue L 6901F, Heliogen®) Blue NBD 7010, Heliogen® BlueK 7090, Heliogen® Blue L 7101F, Paliogen®) Blue L 6470, Heliogen®) GreenK 8683, and Heliogen® Green L 9140. The following black pigments areavailable from Cabot: Monarch® 1400, Monarch® 1300, Monarch®) 1100,Monarch® 1000, Monarch®) 900, Monarch® 880, Monarch® 800, and Monarch®)700. The following pigments are available from CIBA: Chromophtal®)Yellow 3G, Chromophtal®) Yellow GR, Chromophtal®) Yellow 8G, Igrazin®Yellow SGT, Igralite Rubine 4BL, Monastral® Magenta, Monastral® Scarlet,Monastral® Violet R, Monastral® Red B, and Monastral® Violet Maroon B.The following pigments are available from Degussa: Printex® U, Printex®V, Printex® 140U, Printex® 140V, Color Black FW 200, Color Black FW 2,Color Black FW 2V, Color Black FW 1, Color Black FW 18, Color Black S160, Color Black S 170, Special Black 6, Special Black 5, Special Black4A, and Special Black 4. The following pigment is available from DuPont:Tipure®) R-101. The following pigments are available from Heubach:Dalamar® Yellow YT-858-D and Heucophthal Blue G XBT-583D. The followingpigments are available from Clariant: Permanent Yellow GR, PermanentYellow G, Permanent Yellow DHG, Permanent Yellow NCG-71, PermanentYellow GG, Hansa Yellow RA, Hansa Brilliant Yellow 5GX-02, HansaYellow-X, Novoperm® Yellow HR, Novoperm® Yellow FGL, Hansa BrilliantYellow 10GX, Permanent Yellow G3R-01, Hostaperm® Yellow H4G, Hostaperm®Yellow H3G, Hostaperm® Orange GR, Hostaperm® Scarlet GO, and PermanentRubine F6B. The following pigments are available from Mobay: Quindo®Magenta, Indofast® Brilliant Scarlet, Quindo® Red R6700, Quindo® RedR6713, and Indofast® Violet. The following pigments are available fromSun Chemical: L74-1357 Yellow, L75-1331 Yellow, and L75-2577 Yellow. Thefollowing pigments are available from Columbian: Raven® 7000, Raven®5750, Raven® 5250, Raven® 5000, and Raven® 3500. The following pigmentis available from Sun Chemical: LHD9303 Black. Any other pigment and/ordye can be used that is useful in modifying the color of the abovedescribed compositions and/or ultimately, the printed part.

The colorant can be included in the conductive fusing agent compositionand/or the second fusing agent composition to impart color to theprinted object when the fusing agent compositions are jetted onto thepowder bed. Optionally, a set of differently colored fusing agentcompositions can be used to print multiple colors. For example, a set offusing agent compositions including any combination of cyan, magenta,yellow (and/or any other colors), colorless, white, and/or black fusingagent compositions can be used to print objects in full color.Alternatively or additionally, a colorless fusing agent composition canbe used in conjunction with a set of colored, non-fusing agentcompositions to impart color. In some examples, a colorless fusing agentcomposition can be used to coalesce the polymer powder and a separateset of colored or black or white inks not containing a fusing agent canbe used to impart color.

The components of the above described compositions can be selected togive the compositions good jetting performance and the ability to colorthe polymer powder with good optical density. Besides the transitionmetals, fusing agents, colorants and other ingredients described above,the compositions can also include a liquid jetting vehicle. In someexamples, the liquid jetting vehicle formulation can include water andone or more co-solvents present in total at from 1 wt % to 50 wt %,depending on the jetting architecture. Further, one or more non-ionic,cationic, and/or anionic surfactant can optionally be present, rangingfrom 0.01 wt % to 20 wt %. In one example, the surfactant can be presentin an amount from 5 wt % to 20 wt %. The liquid jetting vehicle can alsoinclude dispersants in an amount from 5 wt % to 20 wt %. The balance ofthe formulation can be purified water, or other vehicle components suchas biocides, viscosity modifiers, materials for pH adjustment,sequestering agents, preservatives, and the like. In one example, theliquid jetting vehicle can be predominantly water. In some examples, awater-dispersible or water-soluble fusing agent can be used with anaqueous vehicle. Because the fusing agent is dispersible or soluble inwater, an organic co-solvent is not necessary to solubilize the fusingagent. Therefore, in some examples the compositions can be substantiallyfree of organic solvent. However, in other examples a co-solvent can beused to help disperse other dyes or pigments, or improve the jettingproperties of the compositions. In still further examples, a non-aqueousvehicle can be used with an organic-soluble or organic-dispersiblefusing agent.

In certain examples, a high boiling point co-solvent can be included inthe compositions. The high boiling point co-solvent can be an organicco-solvent that boils at a temperature higher than the temperature ofthe powder bed during printing. In some examples, the high boiling pointco-solvent can have a boiling point above 250° C. In still furtherexamples, the high boiling point co-solvent can be present in thecompositions at a concentration from about 1 wt % to about 4 wt %.

Classes of co-solvents that can be used can include organic co-solventsincluding aliphatic alcohols, aromatic alcohols, diols, glycol ethers,polyglycol ethers, caprolactams, formamides, acetamides, and long chainalcohols. Examples of such compounds include primary aliphatic alcohols,secondary aliphatic alcohols, 1,2-alcohols, 1,3-alcohols, 1,5-alcohols,ethylene glycol alkyl ethers, propylene glycol alkyl ethers, higherhomologs (C₆-C₁₂) of polyethylene glycol alkyl ethers, N-alkylcaprolactams, unsubstituted caprolactams, both substituted andunsubstituted formamides, both substituted and unsubstituted acetamides,and the like. Specific examples of solvents that can be used include,but are not limited to, 2-pyrrolidinone, N-methylpyrrolidone,2-hydroxyethyl-2-pyrrolidone, 2-methyl-1,3-propanediol, tetraethyleneglycol, 1,6-hexanediol, 1,5-hexanediol and 1,5-pentanediol.

One or more surfactants can also be used, such as alkyl polyethyleneoxides, alkyl phenyl polyethylene oxides, polyethylene oxide blockcopolymers, acetylenic polyethylene oxides, polyethylene oxide(di)esters, polyethylene oxide amines, protonated polyethylene oxideamines, protonated polyethylene oxide amides, dimethicone copolyols,substituted amine oxides, and the like. The amount of surfactant addedto the formulation of this disclosure may range from 0.01 wt % to 20 wt%. Suitable surfactants can include, but are not limited to, liponicesters such as Tergitol™ 15-S-12, Tergitol™ 15-S-7 available from DowChemical Company, LEG-1 and LEG-7; Triton™ X-100; Triton™ X-405available from Dow Chemical Company and sodium dodecylsulfate.

Consistent with the formulation of this disclosure, various otheradditives can be employed to optimize the properties of the compositionsfor specific applications. Examples of these additives are those addedto inhibit the growth of harmful microorganisms. These additives may bebiocides, fungicides, and other microbial agents. Examples of suitablemicrobial agents include, but are not limited to, NUOSEPT® (Nudex,Inc.), UCARCIDE™ (Union carbide Corp.), VANCIDE® (R.T. Vanderbilt Co.),PROXEL® (ICI America), and combinations thereof.

Sequestering agents, such as EDTA (ethylene diamine tetra acetic acid),may be included to eliminate the deleterious effects of heavy metalimpurities, and buffer solutions may be used to control the pH of thecompositions. From 0.01 wt % to 2 wt %, for example, can be used.Viscosity modifiers and buffers may also be present, as well as otheradditives to modify properties of the compositions as desired. Suchadditives can be present at from 0.01 wt % to 20 wt %.

The present technology also extends to methods of making 3-dimensionalprinted parts having integrated temperature sensors. The methods can useany of the materials described above. FIG. 6 is a flowchart of anexemplary method 600 of making a 3-dimensional printed part having anintegrated temperature sensor. The method includes dispensing aconductive fusing agent composition onto a first area of a layer ofthermoplastic polymer particles, wherein the conductive fusing agentcomposition includes a transition metal 610; dispensing a second fusingagent composition onto a second area of the layer of thermoplasticpolymer particles, wherein the second fusing agent composition includesa fusing agent capable of absorbing electromagnetic radiation to produceheat 620; fusing the first and second areas with electromagneticradiation to form a resistor in the first area and a part body in thesecond area, wherein the resistor includes a matrix of sinteredtransition metal particles interlocked with a matrix of fusedthermoplastic polymer particles, and the part body includes fusedthermoplastic polymer particles, and wherein the resistor has a positivetemperature coefficient of resistance 630; and connecting a resistancemeasuring device to the resistor to measure a resistance of the resistor640.

In further examples, methods of making 3-dimensional printed partshaving integrated temperature sensors can include dispensing additionalcompositions onto the thermoplastic polymer particles. For example, apretreat composition can be dispensed onto the polymer particles beforedispensing the conductive fusing agent composition. The pretreatcomposition can include a halogen salt such as sodium chloride orpotassium chloride to remove dispersing agents from the transition metalparticles in the conductive fusing agent composition. Colored inks canalso be dispensed onto the polymer particles to provide visible colorsto the printed part.

In some examples, the fusing agent compositions and other compositionscan be dispensed by fluid jetting. This can be performed by a fluid jetprinting system such as a thermal ink jet printing system or a piezo inkjet printing system. Any other suitable method of dispensing thecompositions onto the polymer particles can also be used.

In additional examples, the methods described herein can be performedusing a powder bed 3-dimensional printing system. In one example, thebed of the thermoplastic polymer particles can be formed by introducingpolymer powder from a polymer powder supply and rolling the powder in athin layer using a roller. The conductive fusing agent composition andsecond fusing agent composition can be jetted using fluid jet printheads. The amount of conductive fusing agent composition printed can becalibrated based on the concentration of transition metal in thecomposition, the temperature boosting capacity of the transition metal,the desired conductivity of the resulting conductive composite materialto be printed, among other factors. Similarly, the amount of the secondfusing agent composition printed can be calibrated based theconcentration of fusing agent, temperature boosting capacity of thefusing agent, and other factors. In some examples, the amount of fusingagent composition printed can be sufficient to saturate the powderlayer, thereby contacting a fused layer below and upon curing forming acontinuous part. For example, if each layer of polymer powder is 100microns thick, then the fusing agent composition can penetrate at least100 microns into the polymer powder. Thus the fusing agents can heat thepolymer powder throughout the entire layer so that the layer cancoalesce and bond to the layer below. After forming a solid layer, a newlayer of loose powder can be formed, either by lowering the powder bedor by raising the height of the roller and rolling a new layer ofpowder.

The entire powder bed can be preheated to a temperature below themelting or softening point of the polymer powder. In one example, thepreheat temperature can be from about 10° C. to about 30° C. below themelting or softening point. In another example, the preheat temperaturecan be within 50° C. of the melting of softening point. In a particularexample, the preheat temperature can be from about 160° C. to about 170°C. and the polymer powder can be nylon 12 powder. In another example,the preheat temperature can be about 90° C. to about 100° C. and thepolymer powder can be thermoplastic polyurethane. Preheating can beaccomplished with one or more lamps, an oven, a heated support bed, orother types of heaters. In some examples, the entire powder bed can beheated to a substantially uniform temperature.

The powder bed can be irradiated with a fusing lamp. Suitable fusinglamps for use in the methods described herein can include commerciallyavailable infrared lamps and halogen lamps. The fusing lamp can be astationary lamp or a moving lamp. For example, the lamp can be mountedon a track to move horizontally across the powder bed. Such a fusinglamp can make multiple passes over the bed depending on the amount ofexposure needed to coalesce each printed layer. The fusing lamp can beconfigured to irradiate the entire powder bed with a substantiallyuniform amount of energy. This can selectively coalesce the printedportions with fusing agent compositions leaving the unprinted portionsof the polymer powder below the melting or softening point.

In one example, the fusing lamp can be matched with the fusing agents inthe fusing agent compositions so that the fusing lamp emits wavelengthsof light that match the peak absorption wavelengths of the fusingagents. A fusing agent with a narrow peak at a particular near-infraredwavelength can be used with a fusing lamp that emits a narrow range ofwavelengths at approximately the peak wavelength of the fusing agent.Similarly, a fusing agent that absorbs a broad range of near-infraredwavelengths can be used with a fusing lamp that emits a broad range ofwavelengths. Matching the fusing agent and the fusing lamp in this waycan increase the efficiency of coalescing the polymer particles with thefusing agent printed thereon, while the unprinted polymer particles donot absorb as much light and remain at a lower temperature.

Depending on the amount of fusing agent present in the polymer powder,the absorbance of the fusing agent, the preheat temperature, and themelting or softening point of the polymer, an appropriate amount ofirradiation can be supplied from the fusing lamp. In some examples, thefusing lamp can irradiate each layer from about 0.5 to about 10 secondsper pass.

In further examples, methods of making 3-dimensional printed partshaving integrated temperature sensors can include tuning the resistanceof the 3-dimensional printed resistor to a desired range. As explainedabove, the resistor can have the form of a conductive composite with amatrix of fused thermoplastic polymer particles interlocked with amatrix of sintered transition metal particles. The resistance of theconductive composite can be tuned in a variety of ways. For example, theresistance can be affected by the type of transition metal in theconductive fusing agent composition, the concentration of the transitionmetal in the conductive fusing agent composition, the amount ofconductive fusing agent composition dispensed onto the powder bed, thecross section and length of the resistor, and so on. When the conductivefusing agent composition is dispensed by fluid jetting, the amount ofconductive fusing agent composition dispensed can be adjusted bychanging print speed, drop weight, number of slots from which thecomposition is fired in the fluid jet printer, and number of passesprinted per powder layer. In certain examples, a conductive compositeelement can have a resistance from 1 ohm to 5 Mega ohms.

Sufficient conductivity can be achieved by dispensing a sufficientamount of the transition metal onto the powder bed. In some examples, asufficient mass of the transition metal per volume of the conductivecomposite can be used to achieve conductivity. For example, the mass oftransition metal per volume of conductive composite can be greater than1 mg/cm³, greater than 10 mg/cm³, greater than 50 mg/cm³, or greaterthan 100 mg/cm³. In a particular example, the mass of transition metalper volume of the conductive composite can be greater than 140 mg/cm³.In further examples, the mass of transition metal per volume ofconductive composite can be from 1 mg/cm³ to 1000 mg/cm³, from 10 mg/cm³to 1000 mg/cm³, from 50 mg/cm³ to 500 mg/cm³, or from 100 mg/cm³ to 500mg/cm³.

In certain examples, a smaller amount of transition metal can bedispensed to achieve surface conductivity, and a larger amount oftransition metal can be applied to achieve bulk conductivity in theconductive composite. Thus, in some examples a smaller amount ofconductive fusing agent composition can be printed on a single layer ofpolymer particles to form a resistor that has conductivity across thesurface of the layer, i.e., in the x-y plane. In some examples,resistors with conductivity in the x-y plane can be formed with a massof transition metal per volume of conductive composite that is greaterthan 1 mg/cm³ or greater than 10 mg/cm³. In further examples, suchresistors can be formed with a mass of transition metal per volume ofconductive composite from 1 mg/cm³ to 1000 mg/cm³, 10 mg/cm³ to 500mg/cm³, or 30 mg/cm³ to 200 mg/cm³. However, such resistors may not havesufficient conductivity in the z-axis direction, or in other words,through the bulk of the layer. As used herein, the “z-axis” refers tothe axis orthogonal to the x-y plane. For example, in 3-dimensionalprinting methods that use a powder bed that lowers after each layer isprinted, the powder bed is lowered in the z-axis direction.

In some examples, a resistor that is conductive only in the x-y planecan be sufficient. This is the case when the resistor is formed parallelto the layers of the 3-dimensional printed part. However, methodsaccording to the present technology can also be used to print resistorsthat are conductive in the z-axis direction. By dispensing a largeramount of conductive fusing agent composition onto the layer of polymerparticles, the conductive fusing agent composition can penetrate throughthe layer and conductivity between layers in the z-axis direction can beachieved. In some examples, resistors that are conductive in the z-axisdirection can be formed with a mass of transition metal per volume ofconductive composite that is greater than 50 mg/cm³ or greater than 100mg/cm³. In further examples, such resistors can be formed with a mass oftransition metal per volume of conductive composite from 50 mg/cm³ to1000 mg/cm³, 100 mg/cm³ to 1000 mg/cm³, or 140 mg/cm³ to 500 mg/cm³.

In some examples, the amount of transition metal dispensed onto thepowder bed can be adjusted by printing the conductive fusing agentcomposition in multiple passes. In one example, a single pass of a fluidjet print head can be sufficient to dispense enough transition metal toachieve surface conductivity. However, in some cases, a single pass isnot sufficient to achieve conductivity in the z-axis direction.Additional passes can be applied to increase the amount of transitionmetal in the transition metal composite, until a sufficient conductivityin the z-axis direction is achieved. In one example, three or morepasses can be used to form a conductive composite with conductivity inthe z-axis direction. In further examples, the amount of transitionmetal dispensed can be adjusted by adjusting the drop weight of thefluid jet printhead either through resistor design or by changing firingparameters. Thus, with a greater drop weight, a greater amount of theconductive fusing agent composition can be printed with each drop fired.However, in some cases jetting too large an amount of the composition ina single pass can lead to lower print quality because of spreading.Furthermore, adding a large amount of fluid in a single pass can bethermally disruptive, leading to excessive cooling of the print and partdeformation due to polymer recrystallization. Therefore, in someexamples multiple passes can be used to print a sufficient concentrationof the conductive fusing agent composition with better print quality.This can also prevent excessive part cooling and avoid part deformation.

In a particular example, a 3-dimensional printed part can be formed asfollows. A fluid jet printer can be used to print a first pass includingprinting a conductive fusing agent composition onto a first portion ofthe powder bed and printing a second fusing agent composition onto asecond portion of the powder bed. A curing pass can then be performed bypassing a fusing lamp over the powder bed to fuse the polymer particlesand sinter transition metal particles in the conductive fusing agentcomposition. Then, one or more additional passes can be performed ofprinting the conductive fusing agent composition onto the first portionof the powder bed to increase the amount of transition metal. Each passof printing the conductive fusing agent composition can be followed by acuring pass with the fusing lamp. In another example, multiple passes ofprinting the conductive fusing agent composition onto a powder layerwithout fully fusing the powder layer between printed passes. This canallow the conductive fusing agent so saturate the polymer powder beforethe powder layer becomes fused. The number of passes used can depend onthe desired conductivity, the contone level of the printing passes(referring to the density of conductive fusing agent composition perarea deposited on each pass), the type of transition metal in theconductive fusing agent composition, concentration of transition metalin the conductive fusing agent composition, thickness of the layer ofpolymer powder being printed, and so on.

Accordingly, the methods of the present technology can be used to make3-dimensional printed parts with integrated temperature sensors that areoriented in any direction. As explained above, a resistor can be formedin the x-y plane with respect to the layers of the 3-dimensional printedpart using a relatively smaller amount of conductive fusing agentcomposition, while resistors oriented in the z-axis direction can beformed by using a relatively greater amount of conductive fusing agentcomposition on each layer. In one example, the resistor can be orientedat least partially in the z-axis direction with respect to the layers ofthe 3-dimensional printed part. As used herein, “at least partially inthe z-axis direction” refers to any direction that has at least anon-zero component on the z-axis. Therefore, resistors can be formedparallel to the z-axis or diagonal to the z-axis using the methodsdescribed herein.

The 3-dimensional printing methods described herein can be used tomanufacture a wide variety of complex part shapes. The resistors printedas integrated temperature sensors can similarly have a wide variety ofshapes. In some examples, the resistor can have a serpentine shape withmultiple turns along the length of the resistor. In some cases,increasing the length of the resistor can increase the overallresistance. Other resistor shapes can also be used.

3-dimensional printed parts can also be made with multiple integratedresistors. For example, multiple resistors can be included to measuretemperature on multiple portions of the part.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise.

As used herein, “liquid jetting vehicle,” “liquid vehicle” or “inkvehicle” refers to a liquid fluid in which fusing agents can be placedto form jettable fusing agent compositions. Colorants can also be addedto liquid jetting vehicles to form colored inks. A wide variety ofvehicles may be used with the systems and methods of the presentdisclosure. Such vehicles may include a mixture of a variety ofdifferent agents, including, surfactants, solvents, co-solvents,anti-kogation agents, buffers, biocides, sequestering agents, viscositymodifiers, surface-active agents, water, etc. Though not part of theliquid vehicle per se, in addition to the colorants and fusing agents,the liquid vehicle can carry solid additives such as polymers, latexes,UV curable materials, plasticizers, salts, etc.

As used herein, “colorant” can include dyes and/or pigments.

As used herein, “dye” refers to compounds or molecules that absorbelectromagnetic radiation or certain wavelengths thereof. Dyes canimpart a visible color to an ink if the dyes absorb wavelengths in thevisible spectrum.

As used herein, “pigment” generally includes pigment colorants, magneticparticles, aluminas, silicas, and/or other ceramics, organo-metallics orother opaque particles, whether or not such particulates impart color.Thus, though the present description primarily exemplifies the use ofpigment colorants, the term “pigment” can be used more generally todescribe not only pigment colorants, but other pigments such asorganometallics, ferrites, ceramics, etc. In one specific aspect,however, the pigment is a pigment colorant.

As used herein, “soluble,” refers to a solubility percentage of morethan 5 wt %.

As used herein, “fluid jetting” or “jetting” refers to compositions thatare ejected from fluid jetting architecture, such as ink-jetarchitecture. Fluid jetting architecture can include thermal or piezoarchitecture. Additionally, such architecture can be configured to printvarying drop sizes such as less than 10 picoliters, less than 20picoliters, less than 30 picoliters, less than 40 picoliters, less than50 picoliters, etc.

As used herein, the term “substantial” or “substantially” when used inreference to a quantity or amount of a material, or a specificcharacteristic thereof, refers to an amount that is sufficient toprovide an effect that the material or characteristic was intended toprovide. The exact degree of deviation allowable may in some casesdepend on the specific context.

As used herein, the term “about” is used to provide flexibility to anumerical range endpoint by providing that a given value may be “alittle above” or “a little below” the endpoint. The degree offlexibility of this term can be dictated by the particular variable anddetermined based on the associated description herein.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary.

Concentrations, amounts, and other numerical data may be expressed orpresented herein in a range format. It is to be understood that such arange format is used merely for convenience and brevity and thus shouldbe interpreted flexibly to include not only the numerical valuesexplicitly recited as the limits of the range, but also to includeindividual numerical values or sub-ranges encompassed within that rangeas if each numerical value and sub-range is explicitly recited. As anillustration, a numerical range of “about 1 wt % to about 5 wt %” shouldbe interpreted to include not only the explicitly recited values ofabout 1 wt % to about 5 wt %, but also include individual values andsub-ranges within the indicated range. Thus, included in this numericalrange are individual values such as 2, 3.5, and 4 and sub-ranges such asfrom 1-3, from 2-4, and from 3-5, etc. This same principle applies toranges reciting only one numerical value. Furthermore, such aninterpretation should apply regardless of the breadth of the range orthe characteristics being described.

EXAMPLE

The following illustrates an example of the present disclosure. However,it is to be understood that the following is only illustrative of theapplication of the principles of the present disclosure. Numerousmodifications and alternative compositions, methods, and systems may bedevised without departing from the spirit and scope of the presentdisclosure. The appended claims are intended to cover such modificationsand arrangements.

Example 1

A 3-dimensional printing system was used to print a temperature sensorwith a serpentine shaped resistor embedded in a rectangular polymerstrip. A conductive fusing agent composition, pretreat composition, andsecond fusing agent composition were printed from three separate ink jetslots. The conductive fusing agent composition was a silver ink(Mitsubishi NBSIJ-MU01) containing silver nanoparticles. The silvernanoparticles had an average particle size of approximately 20 nm. Thepretreat composition was a solution of 3 wt % sodium chloride in water.The second fusing agent composition included carbon black as the fusingagent and an aqueous vehicle.

The fusing agent compositions and pretreat composition were jetted ontoa bed of nylon (PA12) particles (Vestosint® x1556). The nylon particleshad an average particle size of approximately 50 μm. The layer thicknesswas approximately 100 μm. Each layer was printed with the pretreatcomposition followed by the conductive fusing agent composition in theportions that make up the resistor, and the carbon black fusing agentcomposition in the insulating portions. The compositions were printed atcontone levels of 255 for the conductive fusing agent composition, 255for the pretreat composition, and 15 for the carbon black fusing agentcomposition. Three (3) passes of the compositions were performed foreach layer. After each pass with the compositions, a curing pass wasperformed. In this example, the amount of solid silver dispensed ontothe powder was 141 mg/cm³ of the powder layer; the amount of chloridesalt dispensed was 23 mg/cm³ of the powder layer; and the amount ofcarbon black dispensed was 2.3 mg/cm³ of the powder layer.

The printer powder supply and powder bed were filled with the nylonparticles. The supply temperature was set at 110° C. and the print bedtemperature was set at 130° C. A heater under the print bed was set at150° C. The print speed was set at 10 inches per second (ips) and thecure speed was set at 7 ips. Curing was performed using two 300 W bulbsplaced approximately 1 cm away from the surface of the powder bed.

After printing the temperature sensor, the temperature sensor was wiredto a HP® 34401 digital multimeter using silver epoxy to create apermanent bond with the sensor contacts. The temperature sensor wasplaced in a temperature controlled Thermotron® SE 2000 oven. Thetemperature of the oven was ramped from 20° C. to 30° C., 40° C., 50°C., 60° C., and then back to 30° C. The resistance of the temperaturesensor as measured by the digital multimeter is plotted in FIG. 7. Theresults show that the resistance of the 3-dimensional printedtemperature sensor has a positive correlation with temperature.

What is claimed is:
 1. A temperature sensor, comprising: a resistorformed of a matrix of sintered elemental transition metal particlesinterlocked with a matrix of fused thermoplastic polymer particles,wherein the resistor has a positive temperature coefficient ofresistance; a first electrical contact at a first end of the resistor; asecond electrical contact at a second end of the resistor; and aresistance measuring device connected to the first electrical contactand the second electrical contact to measure a resistance of theresistor.
 2. The temperature sensor of claim 1, wherein the elementaltransition metal particles comprise silver particles, copper particles,gold particles, or combinations thereof.
 3. The temperature sensor ofclaim 1, wherein the matrix of fused thermoplastic polymer particlescomprises a fusing agent selected from carbon black, a near-infraredabsorbing dye, a near-infrared absorbing pigment, a tungsten bronze, amolybdenum bronze, metal nanoparticles, a conjugated polymer, orcombinations thereof.
 4. The temperature sensor of claim 1, wherein theresistor further comprises a halogen salt in the matrix of sinteredelemental transition metal particles, the matrix of fused thermoplasticpolymer particles, or both.
 5. The temperature sensor of claim 1,wherein the resistor has a resistance from 1 ohm to 1 Mega ohm.
 6. A3-dimensional printed part having an integrated temperature sensor,comprising: a part body formed of fused thermoplastic polymer particles;a resistor formed of a matrix of sintered elemental transition metalparticles interlocked with a matrix of fused thermoplastic polymerparticles, wherein the matrix of fused thermoplastic polymer particlesis continuously fused to the fused thermoplastic polymer particles ofthe part body, and wherein the resistor has a positive temperaturecoefficient of resistance; a first electrical contact at a first end ofthe resistor; a second electrical contact at a second end of theresistor; and a resistance measuring device connected to the firstelectrical contact and the second electrical contact to measure aresistance of the resistor.
 7. The 3-dimensional printed part of claim6, wherein the elemental transition metal particles comprise silverparticles, copper particles, gold particles, or combinations thereof. 8.The 3-dimensional printed part of claim 6, wherein the fusedthermoplastic polymer particles comprise a fusing agent selected fromcarbon black, a near-infrared absorbing dye, a near-infrared absorbingpigment, a tungsten bronze, a molybdenum bronze, metal nanoparticles, aconjugated polymer, or combinations thereof.
 9. The 3-dimensionalprinted part of claim 6, wherein the resistor further comprises ahalogen salt in the matrix of sintered elemental transition metalparticles, the matrix of fused thermoplastic polymer particles, or both.10. The 3-dimensional printed part of claim 6, wherein the resistor hasa resistance from 1 ohm to 1 Mega ohm.
 11. The 3-dimensional printedpart of claim 6, wherein the resistor is embedded in the part body. 12.The 3-dimensional printed part of claim 6, wherein the part is formed ofmultiple layers of fused thermoplastic polymer particles stacked in az-axis direction, and wherein the resistor is oriented at leastpartially in the z-axis direction.
 13. A method of making a3-dimensional printed part having an integrated temperature sensor, themethod comprising: dispensing a conductive fusing agent composition ontoa first area of a layer of thermoplastic polymer particles, wherein theconductive fusing agent composition comprises a transition metal;dispensing a second fusing agent composition onto a second area of thelayer of thermoplastic polymer particles, wherein the second fusingagent composition comprises a fusing agent capable of absorbingelectromagnetic radiation to produce heat; fusing the first and secondareas with electromagnetic radiation to form a resistor in the firstarea and a part body in the second area, wherein the resistor comprisesa matrix of sintered transition metal particles interlocked with amatrix of fused thermoplastic polymer particles, and the part bodycomprises fused thermoplastic polymer particles, and wherein theresistor has a positive temperature coefficient of resistance; andconnecting a resistance measuring device to the resistor to measure aresistance of the resistor.
 14. The method of claim 13, wherein theresistor is embedded in the part body.
 15. The method of claim 13,wherein the transition metal is in the form of elemental transitionmetal particles.